Parent Company Information - Statements Of Cash Flows (Details) - USD ($) $ in Thousands	3 Months Ended								12 Months Ended
	Dec. 31, 2016	Sep. 30, 2016	Jun. 30, 2016	Mar. 31, 2016	Dec. 31, 2015	Sep. 30, 2015	Jun. 30, 2015	Mar. 31, 2015	Dec. 31, 2016	Dec. 31, 2015	Dec. 31, 2014
Operating Activities:
Net income attributable to Northrim BanCorp, Inc.	$ 3,590	$ 3,095	$ 4,350	$ 3,376	$ 4,106	$ 5,335	$ 4,781	$ 3,561	$ 14,411	$ 17,783	$ 17,408
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Stock-based compensation									778	608	360
Net Cash Provided by Operating Activities									20,123	10,519	20,478
Investing Activities:
Purchases of investment securities available for sale									(145,707)	(210,308)	(264,943)
Net cash received from Alaska Pacific acquisition									0	0	6,367
Net Cash Used by Investing Activities									(47,499)	(63,339)	(48,658)
Financing Activities:
Dividends paid to shareholders									(5,372)	(5,117)	(4,750)
Net Cash Provided by Financing Activities									19,254	42,937	11,145
Net Decrease in Cash and Cash Equivalents									(8,122)	(9,883)	(17,035)
Cash and Cash Equivalents at Beginning of Year				58,673				68,556	58,673	68,556	85,591
Cash and Cash Equivalents at End of Year	50,551				58,673				50,551	58,673	68,556
Northrim Bancorp, Inc.
Operating Activities:
Net income attributable to Northrim BanCorp, Inc.									14,411	17,783	17,408
Adjustments to Reconcile Net Income to Net Cash Provided by Operating Activities:
Equity in undistributed earnings from subsidiaries									(15,396)	(19,005)	(19,525)
Stock-based compensation									778	608	360
Changes in other assets and liabilities									(1,458)	(298)	(241)
Net Cash Provided by Operating Activities									(1,665)	(912)	(1,998)
Investing Activities:
Purchases of investment securities available for sale									(1,373)	(3,549)	0
Proceeds from sales/calls/maturities of securities available for sale									0	2,998	0
Net cash received from Alaska Pacific acquisition									0	0	6,367
Investment in Northrim Bank, NISC, NCT1 & NST2									10,115	9,842	(3,000)
Net Cash Used by Investing Activities									8,742	9,291	3,367
Financing Activities:
Dividends paid to shareholders									(5,372)	(5,117)	(4,750)
Proceeds from issuance of common stock and excess tax benefits									0	106	150
Net Cash Provided by Financing Activities									(5,372)	(5,011)	(4,600)
Net Decrease in Cash and Cash Equivalents									1,705	3,368	(3,231)
Cash and Cash Equivalents at Beginning of Year				$ 10,258				$ 6,890	10,258	6,890	10,121
Cash and Cash Equivalents at End of Year	$ 11,963				$ 10,258				$ 11,963	$ 10,258	$ 6,890